Portable exercise machine

ABSTRACT

A light weight portable exercise machine is provided for maintaining cardiovascular tone and for rehabilitation of hospital patients confined to bed. Portability and versatility of the machine are enhanced by a mounting frame which is a part of the unit. Light but sustained exercise is accomplished through pedal operation by the feet and legs of the patient while holding the hands to bars on the frame. A number of permanent magnets are moved into exact juxtaposition opposite other magnets in progressive settings across a modified Faraday disc at a plurality of indented positions, and these magnets, with augmented inertia from a heavy rim, serve to achieve prescription exercise amounts for prescription exercise durations automatically terminated at set limits.

[111 3,831,942 Aug. 27, 1974 PORTABLE EXERCISE MACHINE [75] Inventor: Bruce E. Del Mar, Los Angeles,

Calif.

[73] Assignee: Del Mar Engineering Laboratories,

Los Angeles, Calif.

[22] Filed: Feb. 13, 1973 [21] Appl. No.: 332,149

[52] U.S. Cl. 272/73, 310/105 [51] Int. Cl A63b 23/04 [58] Field of Search 272/73; 73/379, 380, 381; 188/158, 164; 192/84 PM; 310/74, 77, 78,

1,802,437 5/1970 Germany 272/73 Primary Examiner-Richard C. Pinkham Assistant Examiner-R. T. Stouffer Attorney, Agent, or Firm-Jessup & Beecher ABSTRACT A light weight portable exercise machine is provided for maintaining cardiovascular tone and for rehabilitation of hospital patients confined to bed. Portability and versatility of the machine are enhanced by a mounting frame which is a part of the unit. Light but sustained exercise is accomplished through pedal operation by the feet and legs of the patient while holding the hands to bars on the frame. A number of permanent magnets are moved into exact juxtaposition opposite other magnets in progressive settings across a modified Faraday disc at a plurality of indented positions, and these magnets, with augmented inertia from a heavy rim, serve to achieve prescription exercise amounts for prescription exercise durations automatically terminated at set limits.

6 Claims, 12 Drawing Figures 3.931.942 I v I PAIimtnmmn smanre swkza \LJZ//////////////////\T PAIENIEMsamu v 3,331,942

PORTABLE EXERCISE MACHINE BACKGROUND OF THE INVENTION Prolonged exercise has become a widely used method for maintaining and building health, as well as for rehabilitation purposes, by both laymen and professionals. Such exercise is used for the most part in cardiovascular conditioning, where muscular work done by large muscles of the body causes an increased load on the cardiovascular, respiratory and metabolic systems. To be effective, this work must require an appreciable fraction of the maximum power available from the body. Furthermore, the work must be of such a nature that it can be continued for many minutes. To be safe and effective, especially in the case of convalescent patients, and others with compromised physiological systems, the work load must be precisely repeatable and accurately quantified. Finally, since many patients are bedridden, the instrument by which the work is done must be compact and light enough to be carried from bed to bed in the hospital.

It has been found that once a patient becomes bedridden he rapidly loses the cardiovascular tone, and a loss in the normal flow of blood in the lower extremities of the body, the feet and legs. Even without disease, in-

fection, anesthesia, or operative shock, the inactive pa-- tient begins to lose his cardiovascular health, and he is soon unable to get up and walk without noting a great loss of his perambulatory work capability. If the patients perambulatory muscular and cardiovascular health is to be maintained, he needs a form of exercise that meets the requirements of his confinement and the physiological needs of his circulatory system. If his perambulatory muscular and cardiovascular health has become lost because of incapacitative illness or operation, then he needs effective rehabilitation.

Exercise applied to the calf muscles of the leg by exerting pressure thereon in alternating cycles by the patient, as during pedalling of a crank ergometer, pumps blood much as a heart assist. Such exercise is a reasonable and logical means of both avoiding deteriorating cardiovascular and muscular health and tone to the bedridden, and it serves an effective means of commencing rehabilitation of the patient early in the recovery to greatly accelerate his return to normal health and work capability. Such exercise is implemented by the instrument of the invention.

Specifically, the invention serves to meet the criteria set forth above. Although a wide variety of exercise machines and crank ergometers have been available for a number of years, all suffer from deficiencies of one type or another, and none meets all the aforesaid re quirements. Particularly, prior art crank ergometers are not convenient for use in bed by the patient lying on his back, nor are they compact or light enough to be easily carried from bed-to-bed. Although wheeled carts and pulley arrangements have been devised to allow inbed use of ergometer-type units, none of these is in any way practical.

There are several widely used forms of bicycle ergometers in the prior art which use the conventional handlebar and seat with a crank and pedal. One type of prior art bicycle ergometer uses a form of friction drag load which forces a roller against a pneumatic bicycle tire. Another prior art type uses a form of electric load, such as an electro-dynamic magnetic brake or an electric generator with a variable load or field current. The first type of prior art ergometer exhibits unstable load settings. The second type of prior art ergometer generates electric power which may be dangerous, particularly to hospitalized patients, who have implants or electrodes attached to their bodies. The second type of prior art ergometer is also unsatisfactory because it requires a high minimum pedal speed before it becomes effective.

Moreover, the measurement of the work done by the patient with the aforesaid prior art ergometers is subject to gross error. These errors include mechanical and electric generator losses which change with temperature, and a work load which is not readily repeatable by fixed settings. The exercise machine of the present invention is particularly constructed to impose known and measurable mechanical work loads on the users musclespLoading is based on the Faraday disc principle operating in conjunction with precision permanent magnets, the relative positions of which are adjustable by novel means to provide resistive forces of exact magnitudes.

It is an established fact that the capability to do work varies considerably among individuals depending, inter alia, upon their age, size, and physical condition. it is also well established that the crank speed of an ergometer which is most comfortable for prolonged exercising periods, likewise, varies among individuals. Therefore, the ability to introduce various work loads at reasonable but different crank rotational speed is a desirable feature in an exercise machine or ergometer to be used for therapeutic purposes. In the present invention, this is accomplished by incorporating calibrated position adjustments, which may be quickly moved to known locations thereby varying the resistive forces on the disc, and as a result, controlling the braking torque, associated with any given crank speed.

It has also been found, that there must be a certain ratio between the inertial and resistive forces in an ergometer for optimum efficiency insofar as the muscles being exercised are concerned. The exercise ergometer of the invention is constructed so that a particular high ratio of inertial to resistive forces is achieved for such optimum efficiency. Efficiency of muscular exercise is poor when a low ratio of inertial force is present. Also that efficiency becomes less if a very high ratio of inertial force to resistive force is attempted. Therefore, it may be stated that there is a range of inertial/resistive force ratios between a lower limit and an upper limit in which optimum efficiency is achieved. Since there is a range of ratios of inertial/resistive forces which achieve optimum efficiency, there is no need in the ergometer to exactly match the ratio with every load. In the present invention a high inertial mass is used to provide the desired ratio to resistive force at the lower limits for heavy force loads and to exceed the lower limit for the smaller force loads. This is accomplished by providing the load disc with a heavy rim.

The ability to accurately accomplish a prescribed exercise program and to repeat it at a later time for comparative purposes is a highly desirable feature. In order that this may be done without constant surveillance, a brake system is incorporated into the apparatus of the invention, whereby the exercise instrument is automatically stopped after the specified exercise program has been completed. This is accomplished by utilizing a mechanical clock mechanism to activate a brake on the loading wheel at the conclusion of the selected time period.

Other features reside in the shape and portability of the ergometer unit to be described, in its independence of external power requirements, its adaptability to utilization by a patient in a prone position, and its ability to be easily placed and to stay in place on the bed held by an adjustable rigid frame. Portability is assured by modular construction of the unit wherein the individual components are light weight and easily assembled together on a bed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of one embodiment of the exercise machine of the invention;

FIG. 2 is a cut-away elevational view of a disc and permanent magnet assembly in one relative position in the apparatus of FIG. 1 on a somewhat enlarged scale;

FIG. 2A is a further cut-away elevational view of the assembly of FIG. I with multiple pole permanent magnets installed;

FIG. 3 is a cut-away elevational view of the disc and the permanent magnet load assembly of FIG. 2 in another relative position;

FIG. 4 is a section of a component of the permanent magnet load assembly taken along the line 4-4 of FIG.

FIG. 5 is a curve useful in explaining the performance characteristics of the apparatus of FIG. 1;

FIG. 6 is a perspective cut-away view of another embodiment of a stationary permanent magnet assembly for use in the exercise machine;

FIG. 7 is a cut-away plan view of the stationary permanent magnet assembly of FIG. 6;

FIGS. 8 and 9 are operational representations of the embodiment of FIG. 6;

FIG. 10 is a perspective cut-away view of the clockdriven spring release mechanism for use in conjunction with the apparatus of FIG. 1; and

FIG. 11 is a perspective representation of one embodiment of the invention in which the ergometer unit of FIG. 1 is incorporated into a frame to be used on a hospital bed with the patient lying on his back.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS As mentioned above, the ergometer of the invention utilizes an energy absorption concept based on the Faraday disc principle. In the particular embodiment of FIG. I, pedals 10 are connected to a pulley 12; the pulley 12 being coupled to a pulley 16 on a shaft 18 by a belt 14. Pulleys l2 and 16 may be toothed and belt 14 may also be toothed for a more positive drive. Disc assembly 20 is keyed to shaft 18, and a permanent magnet assembly is magnetically coupled to disc assembly 20 so as to form an eddy current brake. In the embodiment of FIG. I, the permanent magnet assembly comprises stationary magnet sub-assembly 24, and a rotatable magnet sub-assembly 26, the sub-assembly 26 providing a capability to adjust the restrictive forces on the disc 20. The disc assembly 20 consists of a current conducting disc 28 and heavy metal rim 30 to provide sufficient mass to create an augmented flywheel effect.

It is desirable to use permanent magnets in the disc ergometer of the invention, not only because of their stability but also in order to avoid the need for external power supplies and wiring associated with electromagnets or generators. However, one major problem in the use of permanent magnets is to provide the capability to vary the load in a broad controllable manner particularly on a compact disc assembly. A magnet assembly arranged to provide a fixed flux field adjacent a Faraday disc can be moved radially outward to provide adjustment, but then there is at best a limited adjustment range and an ungainly size of disc. This problem is overcome in the present invention by incorporation of permanent magnet assemblies capable of being easily adjusted so as to provide varied flux field strengths at the disc. The permanent magnet assembly of the present invention can be such as to provide matching pairs of magnets with opposing poles preferably on opposite sides of the disc maintaining a fixed radial distance from the rotational center of the disc but varying the relative position of opposing magnets either by (a) rotational separation around the disc or .(b) by axial separation from the disc.

With reference to the first arrangement a suggested above for adjusting the flux field, the permanent magnet assembly shown in FIGS. 1, 2, 2A and 3 comprises a stationary magnet sub-assembly 24, and an angular adjustable magnet sub-assembly 26. As shown, these magnet sub-assemblies are mounted on opposite sides of the disc 20. In each of these sub-assemblies, a number of permanent magnets 27 (FIG. 2A) are firmly fixed on the same radius and positioned such that poles of the magnets in one sub-assembly are opposite from the poles in the other sub-assembly. In the examples of FIGS. 2 and 3, the permanent magnets 27 in the adjustable magnet sub-assembly 26 are positioned such that the North poles are nearest the shaft 18, while in the stationary magnet sub-assembly 24, the permanent magnets are positioned such that the South poles are nearest the shaft 18.

While the magnet sub-assembly 24 is held stationary in its pre-selected position by a mounting to the frame structure, the magnet sub-assembly 26 is mounted on shaft 18 with a low friction bearing 32 and is free to be turned to selected angular positions about the shaft. Retention of the adjustable magnet sub-assembly 26 in a desired position is accomplished by including a spring loaded plunger 38 (FIG. 4) in the end portion 36 of sub-assembly 26, and the incorporation on the frame of a locating device such as the detent plate 34 shown in FIGS. 1, 2 and 3. The detent plate may be supported on the frame by any appropriate means. It has indentations 40 (FIG. 4) which cooperate with the plunger 38 for positive positioning. Details of one suitable arrangement are shown in FIG. 4 wherein the rotatable magnet sub-assembly is held in a desired position by the action of the plunger 38 contained in the plate 36 being held in one of the indentations 40 in detent plate 34 by a force of spring 42. The magnitude of the spring force is held to a nominal value so that application of a reasonable force on handle 44 attached to plate 36 as shown in FIGS. 1, 3 and 3 and extending to the exterior of the units housing will result in the spring force being overcome, plunger 38 being moved out of the indentation 40 allowing for repositioning of the magnet subassembly 26 to another desired position.

} One desirable position of the rotatable magnet subassembly 26 relative to stationary magnet sub-assembly 24 is a position whereby one and only one of the permanent magnets in each of the sub-assemblies 24 and 26 are aligned. This condition is shown in FIG. 2, and with the unlike poles of the two magnets opposite one another a certain magnetic field, the strength of which is dependent on among other things the size of the permanent magnets and the air gap between magnets, is established across disc 20. Curve B on FIG. 5 is characteristic of the braking torque developed at various disc rotational speeds under this condition.

If the magnet sub-assembly 26 is rotated to the position shown in FIG. 3, two of the permanent magnets of the sub-assembly 26 are aligned with two of the pennanent magnets of the sub-assembly 24 and with unlike poles opposite, and an increased magnetic field strength across the disc is realized. This can be carried further with three or more permanent magnets in one sub-assembly being aligned with three or more permanent magnets in the other sub-assembly to produce increased torque to rotational speed relationships. As an example, curve C and curve D in FIG. 5 are representative of the braking torque to disc rotational speed relationship with two and three magnets 27 in one subassembly aligned with two and three magnets 27 in the other sub-assembly respectively. Likewise, curve A in FIG. 5 is representative of the braking torque to disc rotational speed relationship when the rotatable magnet sub-assembly 26 is positioned such that none of the magnets are aligned with the minimum torque shown resulting from the stray magnetic field so established.

From FIG. 5, it can readily-be seen that with such an arrangement of permanent magnets, loads of differing magnitudes can be imposed for each rotational speed and conversely, any desired load can be achieved with one of several rotational speeds. In the ergometer of the present invention, these are accomplished by a simple adjustment to the relative position of the permanent magnets easily made by the application of hand movement on handle 44 which also by its position provides an indication of the setting or relative position of the magnets.

Whereas at each magnet mounting location at one side of the disc simple two pole permanent magnets have been shown in the example, the permanent magnets at each mounting location could also have multiple poles as, for example, a pair at 90 to each other or three at 60 as shown in FIG. 2A. In either case, the magnets themselves form a highly efficient magnet circuit in which the magnets themselves provide the return magnetic path.

With reference to the embodiment of FIGS. 6 and 7 for adjusting the flux field strength supplied by pennanent magnets on a Faraday disc to thereby control the braking torque, there is herein shown the means for adjusting the air gap between opposing magnets in a permanent magnet assembly held near the rotating disc. Such an assembly can be as shown in FIGS. 6 and 7 wherein the permanent magnets 49 are mounted for axial movement toward and away from the modified Faraday disc 28. These magnets are held in stationary support anns 51 and 59 on opposite sides of the disc 20. In each of these support arms a number of permanent magnets 49 are installed at the same radial distance from the rotational center of the Faraday disc and these magnets are preferably positioned such that each magnetis directly opposite from a corresponding magnet in the other stationary magnet sub-assembly.

Each magnet is installed in the stationary support arms such that axial movement of the magnet can be effected to bring it close to the disc or far away. This axial movement of the individual permanent magnets can be accomplished with a rotating cam arrangement such as shown in FIG. 7 wherein magnet 49 is fitted into a cylindrical recess drilled in support arms 51 and 59. Magnet 49 may be keyed to a keyway 61 machined in the support arm thereby preventing rotational movement from the desired position. Compression spring 63 can be positioned into the cylindrical recess such that it will bear on both the base of magnet 49 and the support arm. Under the influence of compression spring 63, magnet 49 tends to be displaced closer to the current conducting disc 28 of disc assembly 20.

The freedom of axial movement of magnet 49 is restricted by, and in fact the axial position of magnet 49 is controlled by, the presence of cooperatively engaged cams 65 and 67, the inner-most of which, or cam 65, being firmly fixed to one end of shaft 69 having a fixed length. Cam 67 is firmly attached to magnet 49 to prevent any relative movement between the two parts and shaft 69 passes through an appropriately drilled hole in cam 67. The fixed length of shaft 69 can be assured by insertion of a snap ring 71 into a groove machined into shaft 69 at the appropriate dimension and this snap ring being brought to bear on a surface of the support arm by the force of compression spring 63. Shaft 69 can continue through an appropriately placed hole in exterior panel 73 of the basic exercise machine unit 112 and have attached on the exterior end a knob suitable for rotating shaft 69. Such a knob is shown in FIG. 7 with a knob 75 with a slot 77 included for insertion of some device such as a screwdriver or coin to provide the necessary torque to rotate shaft 69.

As shown in FIGS. 7 and 8, cam 65 and cam 67 are fully meshed allowing magnet 49 to be fully extended by the force of spring 63. Rotation of shaft 69 in either a clockwise or counterclockwise direction causes a retraction of magnet 49 from the fully extended position due to the interaction of the rises on earns 65 and 67 (FIG. 9). With a rotation of shaft 69 or knob 75, cam 65 is rotated such that the lands of this cam are positioned on the lands of the non-rotatable cam 67 (FIG. 9) and, as a result, magnet 49 is in a fully retracted position with the extent of axial movement equal to the rise of the cams.

In the invention as shown in FIG. 6 a multiplicity of permanent magnets are installed in each end of the support arms 51 and 59 at positions of equal radius from the center of disc rotation. The support arms 51 and 59 are held stationary on opposite sides of the disc 20, and they are preferably positioned such that each installed magnet 49 of one is precisely in line with an installed magnet 49 of the other. With the magnets installed in the support anns such that the poles of the magnets in one support arm are opposite from the poles of the magnets in the other support arm, it becomes readily apparent that the strength of the flux field through which the modified Faraday disc assembly 20 rotates can be widely varied by varying the air gap between the individual sets of permanent magnets.

With the opposing magnets in all of the multiplicity of sets fully retracted in support arms, a minimum strength flux field is established due to the relatively large air gap between opposing magnets existing with this condition. When the shafts 69 or knobs 75 on one set of opposing magnets are rotated 90 from the position of fully retracted magnets, the magnets become fully extended with the reduced air gap between magnets greatly increasing the flux field strength between the two magnets.

By establishing the minimum air gap between magnets in a progressive number of the remaining sets of opposing magnets, the total flux field strength through which the disc assembly rotates can be incrementally increased to the maximum attainable. Furthermore, by calibration and setting of the air gaps at each set of magnets to achieve a desired magnitude of field flux, the portable exercise machine can be rapidly set by the operation to achieve prescription exercise loads.

From the above, it can be readily seen that the present invention provides the capability of controlling the setting to known increments of workload, and that this can be accomplished by a simple positioning of knobs 75. With a knob 75 such as shown in FIG. 7, wherein a slot 77 is provided at the exterior of case 73 to effect rotation of the knob and a 90 rotation of the knob is required to cause axial movement of the magnet from one extreme to the other, the angular positions of the slots 77 provide an easily discernable indication of the air gap existing between opposing magnets and therefore the load setting.

Now in order to achieve true therapeutic effect, exercise must be continued for a considerable period of time. To achieve this, the muscles must be presented with a load that is felt physically but one of such nature that rapid fatiguing does not occur. It can be shown that some relatively critical amount of inertia must be combined with a resistive load to allow reasonable mechanical efficiency to be achieved by a muscle. Specifically, in order to prevent fatigue of the muscle, it must be possible to apply forces during the most efficient portion of each cycle, and on a crank type ergometer, forces must be applied together with a sufficiently large amount of inertia to carry the crank over the next half cycle. To allow such efficiency, the moment of inertia must be large enough to match the greatest load. To avoid the large size heavy weight and poor inertia in the typical bicycle ergometer, for example, the mechanical design must be drastically improved. Since moment of inertia varies as the square of an increase in speed, that is gear ratio, the disc must be turned as rapidly as possible relative to input crank speed.

In the embodiment of the invention, such as shown in FIG. 1, the modified Faraday disc is formed, for example, of a copper disc 28 thin enough to allow a narrow air gap between the permanent magnets of the two sub-assemblies 24 and 26, and it is rimmed with a steel rim 30 so that the resulting inertia of the disc 20 at any speed largely offsets the maximum resistance force generated by the permanent magnets. Copper is chosen for the disc 20 to provide high load and efficiency because of its high electrical conductivity. The disc 20 is keyed to shaft 18 which also has the pulley 12 with the positive drive belt 14, the disc 20 is turned as the device is pedalled. By a judicious selection of pulley diameter ratio, the disc is driven at a relatively high speed with a reasonable crank rotational speed. Such an arrangement provides the desired high rotation speed of the disc and the desired high moment of inertia while maintaining size and weight at a minimum.

Another feature of the ergometer of the invention is its ability to display various essential parameters during its use. The displayed parameters are the rotational speed of the Faraday disc 20 in revolutions per minute and the accumulating number of crankv revolutions. As shown in FIG. 1, the rotational speed of the disc 20 is determined by use of a conventional tachometer generator 46 appropriately supported such that its drive wheel is contacted by the disc and is therefore driven at a speed directly proportional to the speed of the disc. The information on disc rotational speed developed by the tachometer generator may be displayed on an indicator 54 incorporated in the present invention such as shown in FIG. 11.

A count of the number of revolutions of the crank can be easily established by incorporation of a simple mechanism such as a cam actuated lever. In such a mechanism as shown in FIG. 1, a lever 52, positioned adjacent to cam 48 attached to pulley shaft 50, is mounted on structure 53 by pin 55 such that the lever is free to pivot about the pin 55. A force, developed by compression spring 57 which is appropriately supported, is continuously applied to lever 52 to assure lever contact with cam 50 at all times. The cam 50 is configured such that the lever 52 moves through one complete cycle for each revolution of the pedals 10. By suitable attachment of a mechanical motion counter 56, such as a Veeder-Root counter or other summing device, to the other end of lever 52, the number of 'revolutions of the cank can be recorded and displayed.

To provide the capability of terminating the exercise program at a prescribed time or work level, a clock activated brake system has been included in the invention. This system consists of a braking device such as shown in FIG. 1, and a clock driven spring release device such as shown in FIG. 10.

In the clock release device of FIG. 10, a conventional mechanical clock mechanism 58 is attached to rear plate 60 with its main shaft 62 passing through appropriate holes in rear plate 60 and forward plate 64. Shaft 62 is supported in these plates by low friction bearings, such as bearing 66, thereby providing rotational freedom. Cam 68 is rigidly attached to shaft 62 intermediate its ends. Attached to the free end of shaft 62 is knob 70 with which, by a clockwise rotation, the clock mechanism can be wound to a preselected time interval. This time interval can be read directly from dial face 72 attached to forward plate 64.

A second shaft 74 is installed between plate 60 and plate 64 and supported in a like manner by low friction bearings, such as bearing 76, to afford unrestricted freedom of rotation. Intermediate ends of shaft 74 is attached pawl 78 including pin 80 as an integral part positioned such that it may be actuated by cam 68 and may engage notch 82 machined in rod 84. A force developed by compression spring 86, suitably attached to upper plate 88 and to pawl 78, assists in maintaining contact between pawl 78 and rod 84. On one end, rod 84 is held in position by sleeve 90 on base plate 92 while retaining its freedom for axial mvoement in a vertical direction. Rod 84 passes through an appropriately placed hole in the upper plate 88 and is attached to arm 92 positioned in a slot in its other end and held by pin 94.

Encompassing a portion of the upper end of rod 84 and retained by plate 88 and arm 92 is compression spring 96 developing a force which tends to move rod 84 in an upward direction or to raise arm 92. One end of arm 92 is attached to plate 64 by use of bracket 98 and pin 100. In such an arrangement, the movement of arm 92 is thereby restricted to a pivotal action around pin 100. Arm 92 passes through slot 102, machined in rear plate 60 to allow for vertical movement, and at the other end, has attached handle 104 which extends through the case housing the clock release device and may be used to manually position arm 92. Push rod 106 is attached by use of pin 108 to this end of arm 92 and extends upward through an appropriate hole in the exterior case of the unit.

When the clock release unit 110 of FIG. is assembled with the basic exercise machine unit 1 12 as shown in FIG. 1 1, push rod 106 is passed through a hole in the exterior case of the exercise machine and comes into contact with lever 114 of the braking device shown in FIG. 1. Lever 1 14 is rigidly attached to shaft 116 which has its two ends supported in suitable structure by low friction bearing, such as bearing 118, thereby permitting rotation of shaft 116. On one end of lever 118 is attached tension spring 119 which develops a force tending to maintain contact between rod 106 and lever 114. Whereas rod 106 contacts lever 114 at a point somewhat removed from. the centerline of shaft 116 toward the attachment point of spring 119, belt 120 is firmly attached to the other end of lever 114 by some means, such as rivets 122 shown in FIG. 1. Lever 114 is positioned on shaft 116 such that belt 120 can be routed around disc assembly with the other end of belt 120 securely attached to a suitable structure by use of fitting 124 and rivets 126.

With the mechanism described above, it is apparent that when rod 106 is fully extended as shown in FIG. 1, the force of spring 119 is overcome and lever 114 is rotated into a position whereby belt 120 is held taut thereby bringing a portion of the belt into contact with the exterior surface of rim 30. With the proper belt tension and length of belt in contact with rim 30, adequate friction can be developed to prohibit continued rotation of the disc 20 or pedals 10. In the converse situation, namely when the force of spring 119 is not overcome by rod 106 due to its position, such as when rod 106 is in its fully retracted position, the force developed by spring 119 rotates lever 114 in a direction such that slackness is created in belt 120 and no contact between belt and rim results. In this condition, no impediment to disc 20 or pedal 10 rotation is introduced.

Therefore, the operational conditions of the unit of FIG. 1, whereby it is freely rotatable or locked, is dependent upon the position of the push rod 106. Control over the position of rod 106 is accomplished with the block release device previously described and shown in FIG. 10. As shown, rod 106 is in a fully retracted position and is held in this position by the interaction of cam 78 and notch 82 in rod 84. As previously stated, this rod position results in a slack belt 120 and freedom for the pedals 10 to be rotated. The fully retracted position of rod 106 can be achieved only by rotation of knob 70 clockwise to some position other than zero thereby repositioning the lip on cam 68 such that no contact is made with pin 80 of pawl 78 and then depressing handle 104 until the action of spring 86 forces pawl 78 into notch 82 in rod 84. As stated before, rotation of knob 70 in a clockwise directon winds the mechanical clock mechanism 58 with the desired time interval for the clock mechanism to unwind being easily established by reference to dial face 72. As the clock unwinds, shaft 62 and the attached cam 68 and knob 70 rotate in a counterclockwise direction when viewed from the front with the lip on cam 68 approaching contact with pin of pawl 78 as the selected time interval nears completion or the index on knob 70 approaches the zero on dial face 72.

At the conclusion of the selected time interval, the lip on cam 68 engages pin 80 and causes movement such that pawl 78 is rotated about the centerline of shaft 74 overcoming the force of spring 86 and is removed from notch 82 of rod 84. With the removal of the pawl from the slot, the force of spring 96 causes rod 84 to move in an upward direction. This vertical movement of rod 84 is translated into the full extension of push rod 106 by the pivoting action of arm 92 about pin 100. As previously explained, push rod 106 in the fully extended position acts on lever 114 to brake the disc 20 and cause stoppage of rotation of pedals 10.

In the assembly described above, the desired speed and number of rotations data are presented in a convenient and easily read manner. Utilizing this information, the actual work accomplished during any period may be readily determined by reference to charts provided with each ergometer and the exercise program can be terminated at the prescribed time interval or work load. In each instance, and as mentioned previously, the simply instrumentation, and the use of permanent magnets, renders the ergometer of the described embodimentof the invention completely independent of any external power requirement or external instrumentation, so that the ergometer may be safely used in a wide variety of locations and under a wide variety of conditions.

Also, with the clock release unit 110 and the basic exercise machine unit 112 fabricated as individual units, it becomes apparent that the units may be built as relatively small, self-contained packages which are rugged, light weight and as a result, easily portable. When assembled, the units provide sufficient instrumentation to monitor the subjects performance and the capability automatically to terminate the subjects activity at the conclusion of the prescribed exercise program with the necessary instruments and controls to accomplish this readily accessible. A latch mechanism between units 110 and 112 is included to provide for easy assembly and disassembly of the two units. To enhance portability and stability of the exercise machine when utilized in bed, a light weight transverse frame such as shown in FIG. 11 is included as a separate unit.

In the embodiment shown in FIG. 11, the units 110 and 112 are mounted in a frame of a shape appropriate for use in a hospital bed with the patient lying on his back. In such an assembly, the clock release unit 110 is permanently attached to a pair of cross bars 128, and the machine unit 112 is latched to unit 110 by latches 111, or equivalent fasteners. The clock release unit 110 provides elevation of the pedals 10 such that adequate foot clearance from the bed is realized. As an adjustment associated with the length of the subjects legs, the cross bars 128 slide longitudinally on the spaced and parallel bars of frame 130 to any desired position for leg reach, and are manually clamped into place by clamps 132. The unit 112 may be removed from the unit 110 by releasing the latches 111, and unit 112 may be conveniently carried by a handle 113.

The vertical portion at one end of the frame 130 has rubber pads 136 attached to it which rest against the uprights at the foot of a hospital bed giving resistance and stability to the leg action by the subject. Toward the head end of the bed, the parallel bars of frame 130 have their ends turned up to provide convenient and comfortable handles 138 to be grasped by the subject in a reclining position with his feet on the pedals of the exercise machine.

The invention provides, therefore, an improved, simple and compact ergometer unit whereby desired work loads may be imparted to the body of a patient, or other subject over prolonged periods of time without excessive tiring. With the multiposition permanent magnet assemblies, the desired work load may be achieved at one of several crank speeds. With the novel braking system incorporated, the exercise program can be automatically terminated at the conclusion of a preselected time interval or work load. With the unique disc design and modular construction, a light weight and compact ergometer is possible resulting in a portable unit easily adapted to use by a patient in bed.

Although particular embodiments of the invention have been shown and described, modifications may be made. It is intended in the following claims to cover the modifications which come within the spirit and scope of the invention.

What is claimed is:

1. A portable exercise machineincluding: a rotatable disc of electrically conductive material; pedal means coupled to said disc to impart rotational motion to said disc; a stationary magnet support structure mounted on one side of said disc; an angularly adjustable magnet support structure mounted on the other side of said disc for angular movement about the axis of rotation of said disc; a first magnetic means mounted in said stationary support structure; and second magnetic means mounted in said adjustable magnet support structure, said first and second magnetic means providing a magnetic field across said disc, the strength of said magnetic field being dependent upon the angular position of said adjustable magnet support structure.

2. The portable exercise machine defined in claim 1, in which said first and second magnetic means each comprises a plurality of permanent magnets.

3. The portable exercise machine defined in claim 2, in which said magnets of said first plurality are positioned on said stationary magnet support structure at a particular radius from the axis of rotation of the disc, and said magnets of said second plurality are positioned on said adjustable magnet support structure at said particular radius from the axis of rotation of said disc.

4. The portable exercise machine defined in claim 3, in which said poles of the magnets of the first plurality are opposite from the poles of the magnets of the second plurality.

5. The portable exercise machine defined in claim 4, and which includes adetent assembly coupled to said adjustable support structure .to permit said adjustable magnet support structure to be turned to predetermined angular positions so as to permit varying numbers of the permanent magnets of the first and second plurality to be aligned with one another for varying the magnetic field strength across the disc.

6. The portable exercise machine defined in claim .1, in which the disc is formed of copper, and which includes a steel rim surrounding said disc and of high mass relative to the mass of the disc. 

1. A portable exercise machine including: a rotatable disc of electrically conductive material; pedal means coupled to said disc to impart rotational motion to said disc; a stationary magnet support structure mounted on one side of said disc; an angularly adjustable magnet support structure mounted on the other side of said disc for angular movement about the axis of rotation of said disc; a first magnetic means mounted in said stationary support structure; and second magnetic means mounted in said adjustable magnet support structure, said first and second magnetic means providing a magnetic field across said disc, the strength of said magnetic field being dependent upon the angular position of said adjustable magnet support structure.
 2. The portable exercise machine defined in claim 1, in which said first and second magnetic means each comprises a plurality of permanent magnets.
 3. The portable exercise machine defined in claim 2, in which said magnets of said first plurality are positioned on said stationary magnet support structure at a particular radius from the axis of rotation of the disc, and said magnets of said second plurality are positioned on said adjustable magnet support structure at said particular radius from the axis of rotation of said disc.
 4. The portable exercise machine defined in claim 3, in which said poles of the magnets of the first plurality are opposite from the poles of the magnets of the second plurality.
 5. The portable exercise machine defined in claim 4, and which includes a detent assembly coupled to said adjustable support structure to permit said adjustable magnet support structure to be turned to predetermined angular positions so as to permit varying numbers of the permanent magnets of the first and second plurality to be aligned with one another for varying the magnetic field strength across the disc.
 6. The portable exercise machine defined in claim 1, in which the disc is formed of copper, and which includes a steel rim surrounding said disc and of high mass relative to the mass of the disc. 